JP2848609B2 - Logic circuit conversion method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention embodies a functional module in logic circuit data configured on a memory of a computer in an automatic logic circuit synthesis system. The present invention relates to a logic circuit conversion method.

(Prior Art) With the enlargement of digital systems, various automatic logic synthesis systems intended to improve design efficiency have been developed. These are automatically synthesized by inputting an operation description of a logic circuit to be designed in a hardware description language or a drawing showing a function of a logic circuit configured using function blocks such as selectors, decoders, and additions, which are called function diagrams, as inputs. In the synthesis process, a process of generating an initial circuit including a functional module from a hardware description and a functional diagram, simplification of logic for the initial circuit generated in this process, real logic elements ( It is roughly divided into a process of performing conversion such as assignment of an element prepared as a library of standard cells or the like and generating an actual physical circuit.

Here, in the latter process, a method is usually employed in which a logic element corresponding to a functional module such as a selector, a decoder, an adder or the like is searched from a cell library and assigned. However, in an operation description or a functional diagram of hardware which is an input of the logic synthesis system, as an operand of an operator or a function (for example, = (assignment), + (addition) of hardware description) corresponding to the functional module, The input of the above functional module may be a constant value of 0 or 1 by writing a constant value or by a process of simplifying logic synthesis. When a corresponding element in the cell library is assigned, “1
There is a problem that a circuit having redundancy such as "one data input is fixed to 0" is generated.

(Problems to be Solved by the Invention) As described above, the conventional method has a disadvantage that a circuit with redundancy is generated when a functional module in logic synthesis is embodied.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a method of efficiently implementing a functional module in logic synthesis and generating a logic circuit with less redundancy.

[Configuration of the invention]

(Means for Solving the Problems) The present invention relates to a logic circuit conversion method configured on a memory of a computer and performing circuit conversion on a logic circuit including a function module, wherein an input signal to a function module included in the logic circuit is provided. Value (for example, whether it is a constant value or not)
Based on the first circuit conversion rule that assigns a logic element (for example, a cell) corresponding to the function module from a library prepared in advance and allocates a logic element (for example, a gate or the like) after developing and optimizing the function module Is selected, and the conversion of the functional module is performed based on the selected circuit conversion rule.

In addition, the logic circuit conversion device according to the present invention includes means for storing data of a logic circuit including a function module, and a first circuit conversion rule for selecting and assigning a logic element corresponding to the function module from a library prepared in advance. Means for storing a circuit conversion rule relating to the realization of a functional module, including a second circuit conversion rule for assigning a physical element after expanding and optimizing the functional module, and an input signal to the functional module included in the logic circuit (A) means for selecting any of the stored circuit conversion rules based on the value of (c), and (b) means for converting the functional module based on the selected circuit conversion rule. According to the present invention, the circuit realization method selecting unit checks the connection destination of the input signal of the functional module in the logic circuit, and Appropriate among functional module implementation methods such as "allocate the corresponding functional element in the cell library" and "expand the functional module to AND / OR gates to optimize and allocate the gate cells" The circuit conversion executing means performs circuit conversion according to the materialization method selected by the circuit materialization method selection means. That is, according to the present invention, it is possible to generate an efficient circuit with less redundancy by realizing the functional module not only by the functions of the functional module but also by focusing on the connection relation of the functional module. Become.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of one embodiment of the present invention. Logic circuits generated based on hardware description languages and functional diagrams
It is stored in the logic circuit data storage unit 11. The logic circuit conversion rule storage unit 12 stores a circuit conversion rule relating to a function module realization method. Logic circuit materialization method selector
The selector 13 selects an appropriate one from the rules stored in the logic circuit conversion rule storage 12 based on the result of checking the connection destination of the input signal of each functional module in the logic circuit data.
The circuit conversion execution unit 14 executes the rule selected by the logic circuit embodying method / selection unit 13 and converts the circuit.

Now, the present invention will be described by taking a case where the selector circuit shown in FIG. 2 is embodied as an example. In FIG. 2, 21 to 23 are registers named A, B and C, respectively, 24 is a NOT gate, 2
Reference numerals 5 and 26 denote selectors, and reference numerals 27 and 28 denote external output terminals named O1 and O2, respectively. Here, 25 and 26 are data inputs (D1 to D
4) and control input (C1 to C4), one of C1 to C4 or C3
This is a function module for selecting the data input of D1 to D4 or D3 corresponding to the control input described above. Where 25
It is assumed that the D1 and D3 inputs have constant values of 1,0. It is also assumed that the two rules shown in FIG. 3 are included in the logic circuit conversion rule storage unit as a method of realizing the selector. Rule
Reference numeral 31 denotes a concrete method of searching for a selector cell in a library and assigning it, and rule 32 denotes a method of realizing a selector by an AND / OR gate. FIG. 4 shows an example of the function and area of the cell registered in the library (integrated to show the magnitude relation). The logic circuit realizing method selecting unit 13 selects one of the rules 31 and 32 regarding the materializing method of the selector according to the algorithm shown in FIG. That is,
Check the connection destination of the selector's data input pin. If the number of constant values is greater than 1/3 of all data inputs, the selector cell is not used and the method is implemented with an AND / OR gate (Rule 32) Is adopted. The circuit conversion execution unit 14 takes out the functional modules (here, selectors) in the circuit one by one, and executes the circuit conversion rule selected by the logic circuit embodying method selection unit 13. In the case of the circuit of FIG. 2, first, there are two constant value inputs D1 and D3 to the selector 25, so that M = 2, N = 4 in FIG. Thus, rule 31 is selected, and cell SE3 is assigned. The circuits generated as a result of the execution of these circuit conversion rules are shown in FIG. Here, 61-65 AND / OR selector 25
This is the gate that was achieved as a result of the gate. 61,63 AND
The gate can be deleted for inputting a constant value. Thereafter, when the cell is allocated, the circuit shown in FIG. 7 is finally generated. 7 to 71 are the parts corresponding to the selector of FIG. Assuming that the area of this part is S1, S1 = 3 from FIG.
+ 3 + 4 = 10. On the other hand, if the area is S2 when the cell SE4 is simply assigned to the selector of FIG. 25 (that is, the conventional method in which the rule 32 is applied to all selectors) regardless of the present method, FIG. S2 = 12> S1. Therefore, by selecting a function module embodying method in consideration of an input of a function module (here, a selector) as in the present method, an efficient circuit having a small area can be generated.

Note that the present invention is not limited to the above embodiment. In the above embodiment, the constant value input of the functional module is focused on as a criterion of the logic circuit materialization method selection. However, when a criterion focusing on the same input of the functional module or a criterion focusing on the control input of the functional module is adopted. Is also conceivable. For example, when the register transfer condition is not 1 (the logical sum of the control input of the selector immediately before the register is 1), a feedback loop is formed using the selector cell and the flip-flop by using a flip-flop including a feedback loop. A more efficient circuit can be generated.

Further, in the above embodiment, an example of a method of realizing a selector has been described. However, it is needless to say that the present invention can be applied to other functional modules such as a decoder, a multiplexer, and an adder.

〔The invention's effect〕

As described above, according to the present invention, the realization process of the functional module in the logic synthesis process is performed in consideration of the connection relation of the functional modules in addition to the functions of the functional modules, thereby achieving redundancy. It is possible to generate a less efficient circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of a logic circuit, FIG. 3 is a diagram showing an embodiment of a selector, and FIG. 4 is a diagram of a cell registered in a library. FIG. 5 is a diagram showing an example, FIG. 5 is a diagram showing an algorithm by which the logic circuit materializing method selecting unit 13 selects the selector materializing rule of FIG. 3, and FIG. 6 is a diagram showing a materializing process of the selector of the circuit of FIG. FIG. 7 is a diagram showing a circuit resulting from the algorithm shown in FIG. 5, and FIG. 7 is a diagram showing a circuit finally obtained as a result of logic synthesis from the circuit of FIG. 11: Logic circuit data storage unit, 12: Logic circuit conversion rule storage unit, 13: Logic circuit implementation method selection unit, 14: Circuit conversion execution unit.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G06F 17/50

Claims (3)

(57) [Claims] 1. A logic circuit conversion method configured on a memory of a computer and performing circuit conversion on a logic circuit including a function module, wherein the function module is based on a value of an input signal to the function module included in the logic circuit. A first circuit conversion rule for selecting and assigning a logic element corresponding to the above from a library prepared in advance, and a second circuit conversion rule for assigning a physical element after expanding and optimizing a functional module, A logic circuit conversion method, wherein the function module is converted based on the selected circuit conversion rule. 2. Checking whether the value of the input signal is a constant value, and selecting a circuit conversion rule based on the result.
The logic circuit conversion method according to claim 1. 3. A means for storing data of a logic circuit including a function module, and a first circuit conversion rule and a function module developed by assigning a logic element corresponding to the function module by selecting from a library prepared in advance. Means for storing a circuit conversion rule relating to the realization of a functional module, including a second circuit conversion rule for assigning a physical element after optimization, and storing based on a value of an input signal to the functional module included in the logic circuit A logic circuit conversion device, comprising: means for selecting one of the circuit conversion rules thus selected; and means for converting the functional module based on the selected circuit conversion rule.